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VIII. On tlie Relation of the Physical Properties of Aqueous 

 Solutions to their state of Ionization. By Prof. J. G. Mac- 



Gregor, Dalhousie College, Halifax, N.S.* 



IT has often been pointed out that, according to the dis- 

 sociation or ionization conception of the constitution of 

 a solution of an electrolyte, the difference between the phy- 

 sical properties of one in which ionization is complete and 

 those of the solvent must be compounded additively of the 

 differences produced by the two ions. It would seem to be 

 equally obvious that, in the case of solutions in which the 

 ionization is not complete, the differences referred to must be 

 similarly compounded of those produced by the undisso- 

 ciated molecules and by the free ions ; and if so, it should be 

 possible to express the numerical values of the various pro- 

 perties in terms of the state of ionization. Such an expression 

 would take its simplest form in the case of solutions so dilute 

 that the molecules, dissociated or undissociated, might be 

 regarded as sufficiently far apart to render mutual action 

 between them impossible, and in these circumstances the 

 change produced in the properties of the solvent by the un- 

 dissociated and the dissociated molecules respectively might 

 be expected to be simply proportional to their respective 

 numbers per unit of volume. It is the object of this paper 

 to test the applicability to sufficiently dilute solutions of such 

 an expression, viz., 



F = ? w + k{l-<z)n + l*n, .... (1) 



where P is the numerical value of any property (density &c), 

 V w that of the same property for water under the same phy- 

 sical conditions, n the molecular concentration of the solution, 

 t. e., the number of gramme-equivalents of the dissolved 

 substance per unit volume of the solution, a the ionization- 

 coefficient, an and (1— a)n consequently the numbers of dis- 

 sociated and undissociated gramme-equivalents per unit of 

 volume respectively, and k and I constants, which may be 

 spoken of as ionization-constants, which will vary with the 

 solvent, the substance dissolved, the property to which they 

 apply, the temperature, and the pressure, but not with the 

 concentration of the solution. 



The formula can obviously apply only to properties for 

 which Pu, has a finite value. Thus it is inapplicable to elec- 

 trical resistance, for which F w would have a practically infinite 

 value. 



* Abstract of a paper read before the Nova Scotian Institute of Science. 

 Communicated by the Author. 



